It is generally accepted that gingivitis is the resultant effect of a confrontation between the host inflammatory response to "local etiological factors." Often the degree of host response is proportional to the degree of insult to these tissues; in some cases, a host response (in terms of tissue destruction) is not proportional to an insult. Moreover, a local etiological factor, a causal explantation, is not apparent with respect to the degree of inflammation. Numerous studies oriented towards an explanation of the development of epidermal organ systems, inclusive of gingiva, skin, teeth, etc., have indicated that the acquisition and maintenance of a specific epithelial phenotype is critically dependent upon the adjacent dermis. Epithelia is always avascular and dependent upon diffusion of nutrients from the dermis. Might the diffusion of simple nutrients, e.g., essential amino acids, sugar amines, in terms of quantity and quality, reflect subtle changes in dermal-epidermal diffusion or, in fact, be a reflection of "host resistance." It is quite evident that simple molecules critically regulate rates of mitosis, rates of protein synthesis, renewal of cell organelles, modifications of cell contacts and numerous other metabolic parameters within cells. The diffusion of nutrients from dermis to epidermis may profoundly effect the quality of the nonkeratinized sulcular epithelia and its inherent ability to ultimately interact with the general oral microenvironment. This research approach attempts to employ human gingival sulcular dermal-epidermal interactions in vitro using biochemical techniques to establish amino acid and nucleotide pool sizes within nonkeratinized epithelia and to study the rates of diffusion of labeled nutrients in human biopsies during different stages of normal maturation. This information will provide a molecular index of the inherent differences which occur in normal, maturing gingival sulcus tissues with respect to dermal-epidermal interaction and then evaluate those types of diffusion patterns which reflect patient susceptibility to periodontal disease (gingivitis).